The present invention concerns the production of activated carbon from polymers with aromatic nuclei, in particular styrene-divinylbenzene copolymers.
Activated carbons have long been known and have a wide range of uses in the area of cleaning and purifying flue gases and waste water or sewage, such use being based on the high adsorption capability of the activated carbon. In general activated carbons have a wide adsorption spectrum. Such activated carbons are not optimised for a specific situation of use, but instead are to be inexpensively manufactured as a mass-produced product.
In contrast high-efficiency activated carbons are optimised for specific situations of use and involve correspondingly higher production costs.
It has been known for some years, for the production of activated carbons, to use polymers with aromatic nuclei, in particular styrene-divinylbenzene copolymers, as the staring materials.
EP 0 326 271 B1 discloses the production of activated carbon, in particular from styrene-divinylbenzene copolymers, wherein the copolymer is firstly treated with a large excess of fuming sulphuric acid or oleum for a prolonged period of time. After sulphonation has been effected, the polysulphonated copolymer is washed to remove excess acid and then dried. The activated carbons obtained have a multi-mode pore size distribution, that is to say the disclosed activated carbon simultaneously has pores of different pore sizes, although there is no disclosure of controlling the pore size distribution or appropriate influencing thereof.
WO 96/21616 discloses a process in which a styrene-divinylbenzene copolymer is pyrolysed or subjected to low-temperature carbonisation with 5 to 50% sulphuric acid at a temperature of up to 750.degree. C. In contrast to the polysulphonation of the aromatic nuclei, which is the aim in EP 0 326 271 B1, as a preliminary step for the production of activated carbon, the amount of sulphuric acid to be used in accordance with WO 96/21616 is not even sufficient for complete monosulphonation of all aromatic nuclei. That however results in a comparatively high loss of mass during the pyrolysis operation, which means that the process is comparatively cost-intensive by virtue of the low level of yield. The pore size or the pore size distribution in the case of the activated carbon in accordance with WO 96/21616 are not mentioned.